Fix ‘make clean’ with a file named ‘-.o’

Fix ‘make clean’ with a file named ‘-.o’

Problem reported by T.V Raman in:
https://lists.gnu.org/r/emacs-devel/2018-09/msg00866.html
* Makefile.in (clean, extraclean):
* doc/emacs/Makefile.in (mostlyclean):
* doc/lispintro/Makefile.in (mostlyclean):
* doc/lispref/Makefile.in (mostlyclean):
* doc/misc/Makefile.in (mostlyclean, clean):
* etc/refcards/Makefile (clean):
* lib-src/Makefile.in (mostlyclean, extraclean):
* lib/Makefile.in (clean):
* lwlib/Makefile.in (clean mostlyclean):
* oldXMenu/Makefile.in (clean mostlyclean):
* src/Makefile.in (mostlyclean, extraclean):
* test/Makefile.in (mostlyclean):
Say ‘rm ./*.o’ instead of ‘rm *.o’ to avoid undesirable failure
when a file name begins with ‘-’.